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Infection with HIV and AIDS are devastating worldwide health
problems. Although progress has been outstanding in
discovering the relationship between HIV and AIDS and this
has resulted in dramatically improved treatment in the
developed world, we are still far from effective prevention
or treatment that can be implemented worldwide. Thus the
burden on science to better understand the pathogenic
relationship between virus and host remains. Indeed, there
are some HIV-1 associated pathologies, including HIV-1
associated dementia (HIVD), that simply are not well
explained by the level of viral replication and may not
disappear simply with effective control of replication. The
HIV-1 Tat protein, well-studied for its role in viral
transcription, represents a conspicuous candidate viral
component that mediates a range of HIV pathologies,
including HIVD and Kaposi’s sarcoma. The molecular
mechanisms and amino acid requirements of Tat for these non-LTR
activities remain unclear. Further the full-length Tat101
protein has been understudied relative to the single exon
Tat72 form, particularly for its role in HIV-1 pathogenesis
through regulation of host gene expression. This proposal
seeks to fill that gap. The central hypothesis is that there
is a unique, definable domain within the Tat second exon,
that in the context of the full length protein, is
responsible for full regulation of host genes. Our specific
aims will address this hypothesis by defining the cytokine
genes that respond in the most clearly differential manner
to the two physiologically relevant forms of Tat (Tat72 and
Tat101) in aim 1. This will be followed up in aim 2 by a
rationally targeted deletion mutagenesis approach to grossly
map the amino acid region in the second exon that provides
the added function to the full length protein in regulation
of cytokine genes. Finally, in aim 3, the functional region
identified by the deletion analysis will be fine mapped by
introduction of logically designed individual amino acid
substitutions to test the effect on cytokine gene
regulation. At the conclusion of this study, we will have
significantly advance the field in understanding the
molecular requirements of the second exon of Tat to fully
mediate host gene regulation. We will be in an opportune
position to continue to investigate the pathways by which
Tat contributes to HIV-1 pathogenesis because we will have a
unique set of tools with which to probe the cellular protein
partners that contact the functional element within the Tat
second exon. It is our long range goal to use these tools to
investigate the biological role and significance of the Tat
protein on HIV-1 associated pathologies, particularly HIVD.
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